REGIOSELECTIVITY INVESTIGATION FOR THE PYROLYSIS OF XANTHATES: A COMPUTATIONAL STUDY

2013 ◽  
Vol 12 (07) ◽  
pp. 1350064 ◽  
Author(s):  
PING WU ◽  
JOHNNY TRUONG ◽  
YONGSHUN HUANG ◽  
JIAXING LI
Keyword(s):  
Oxygen Atom ◽  
Computational Study ◽  
Transition States ◽  
Major Product ◽  
Membered Ring ◽  
Computational Results ◽  
Atomic Size ◽  
Rate Determining Step ◽  
Ring Transition State ◽  
Step Mechanism

MP2/6-31+G(d,p)//MP2/6-31G(d) method was employed to investigate the pyrolyses of O -sec-butyl S -methyl xanthate (Chugeav reaction) and S -sec-butyl O -methyl xanthate, which gave regioselective products of E-butene, Z-butene and 1-butene. Both procedures were found to have 13 possible pathways, of which nine pathways would generate the alkene products. For O -sec-butyl S -methyl xanthate, the computational results indicated that the most favorable three pathways corresponded to a two-step mechanism, with the rate-determining step to be a thion sulfur atom involved six-membered ring transition states. The calculated products distribution was consistent with the experimental observations. However, for S -sec-butyl O -methyl xanthate, thiol-participated four-membered ring transition states were found to be more energetically favored than the six-membered ring transition state to produce 1-butene, which can be attributed to a larger sulfur atomic size than an oxygen atom. As the calculation result, only trace amount of 1-butene could be obtained with a major product being E-butene and Z-butene as a minority.

Pyrolysis of (thio)carbonates via computation analysis

2018 ◽  
Vol 17 (06) ◽  
pp. 1850041
Author(s):  
Jingjing Xia ◽  
Abdullah M. Asiri ◽  
Khalid A. Alamry ◽  
Ping Wu ◽  
Zhihao Huang
Keyword(s):  
Transition States ◽  
Membered Ring ◽  
The Other ◽  
Energy Barriers ◽  
Calculation Results ◽  
Computation Analysis ◽  
Step Mechanism ◽  
Pyrolysis Processes

The regioselective production of alkenes from (thio)carbonates was calculated by MP2/6-31G(d) method via pyrolysis processes. Four (thio)carbonates were calculated in this paper. They are S-sec-butyl O-methyl thiocarbonate (I), O-sec-butyl S-methyl thiocarbonate (II), sec-butyl methyl thioncarbonate (III), and sec-butyl methyl dithiocarbonate (IV). Thirteen potential thermolysis routes were revealed for the pyrolysis of each substance, including nine routes to produce regioselective alkenes and four rearrangement/decompose alternatives. Among nine alkene generation routes, six-membered ring transition states via a two-step mechanism required the lowest energy, while the other routes exhibited higher energy barriers. The calculation results demonstrated an alkene distribution hierarchy of 1-butene [Formula: see text] E-butene [Formula: see text] Z-butene for substances I and II, and an order of E-butene [Formula: see text] 1-butene [Formula: see text] Z-butene for substances III and IV.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

An Alternate Energy-Conserved Pathway for the Morita-Baylis-Hillman (MBH) Reaction

2020 ◽  
Author(s):  
Veejendra Yadav
Keyword(s):  
Proton Transfer ◽  
Transition State ◽  
Lower Energy ◽  
Aldol Reaction ◽  
Membered Ring ◽  
Ammonium Ion ◽  
Alternate Energy ◽  
Ring Transition State ◽  
Mbh Reaction

An new overall lower energy pathway for the amine-catalysed Morita-Baylis-Hillman reaction is proposed from computations at the M06-2X/6-311++G(d,p) level. The pathway involves proton-transfer from the ammonium ion to the alkoxide formed from the aldol reaction through a seven-membered ring transition state (TS) structure followed by highly exothermic Hofmann<i> </i>elimination through a five-membered ring TS structure to form the product and also release the catalyst to carry on with the process all over again.

Theoretical Computations on the Pyrolysis of Alkyl (dithio)acetates

2020 ◽  
Vol 17 (3) ◽  
pp. 224-233
Author(s):  
Xun Zhu ◽  
Chen Jian ◽  
Xiuqin Zhou ◽  
Abdullah M. Asiri ◽  
Khalid A. Alamry ◽  
...  
Keyword(s):  
Transition States ◽  
Membered Ring ◽  
Pyrolysis Process ◽  
Alkyl Esters ◽  
Charge Distributions ◽  
Theoretical Analyses

The pyrolysis of methyl alkyl esters I to III and dithioesters IV to VI were theoretically calculated. All possible pyrolysis paths were considered. Both esters and dithioesters presented three potential paths via six-, four- and five-membered ring transition states, respectively. The calculation processes were calculated using MP2/6-31G(d) set. In-depth theoretical analyses were also presented, including NBO related analyses, synchronicities, and charge distributions, to reveal the detailed pyrolysis process.

Metal-Betaine Interactions.XIV. Silver(I) 3-Carboxylato-1-pyridinioacetate Monohydrate, [Ag{C5H4(COO)NCH2.COO}]n.nH2O

1991 ◽  
Vol 44 (12) ◽  
pp. 1783 ◽  
Author(s):  
XM Chen ◽  
TCW Mak
Keyword(s):  
Oxygen Atom ◽  
Water Molecule ◽  
Lattice Water Molecule ◽  
Membered Ring ◽  
Zigzag Chain ◽  
Two Dimensional ◽  
Metal Centre ◽  
Lattice Water ◽  
Dimensional Network ◽  
Tetrahedral Environment

The complex silver(I) 3-carboxylato-1-pyridinioacetate monohydrate, [Ag{C5H4(COO)NCH2.COO}]n.nH2O, crystallizes in space group P21/c (No. 14), with Z-4, a 12.233(6), b 5.049(1), c 14.418(7)Ǻ, and β 94.96(4)°; the structure was refined to RF -0.057 for 1721 observed [I ≥ 3σ(I)] Mo Kα data. The silver(I) atom is coordinated by four carboxylato oxygen atoms in a distorted tetrahedral environment [Ag-O 2.284(5)-2.570(5)Ǻ]. The tridentate acetato group bridges the Ag1 atoms into a zigzag chain featuring an uncommon [Ag2( carboxylato -O,O′)(carboxylato-μ-1,1-O)] six- membered ring, and the coordination sphere about each metal centre is completed by the unidentate aromatic carboxylato group, resulting in a two-dimensional network in the solid. The lattice water molecule forms hydrogen bonds with the uncoordinated oxygen atom of the aromatic carboxylato group [2.755(9)Ǻ] and the coordinated oxygen atom of the acetato group [2.936(9)Ǻ].

scholarly journals Application of β-Phosphorylated Nitroethenes in [3+2] Cycloaddition Reactions Involving Benzonitrile N-Oxide in the Light of a DFT Computational Study

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 26-37
Author(s):  
Karolina Zawadzińska ◽  
Karolina Kula
Keyword(s):  
Density Functional ◽  
Reaction Path ◽  
Computational Study ◽  
Cyano Group ◽  
Cycloaddition Reactions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Reaction Channels ◽  
One Step ◽  
Step Mechanism

The regiochemistry of [3+2] cycloaddition (32CA) processes between benzonitrile N-oxide 1 and β-phosphorylated analogues of nitroethenes 2a–c has been studied using the Density Functional Theory (DFT) at the M062X/6-31+G(d) theory level. The obtained results of reactivity indices show that benzonitrile N-oxide 1 can be classified both as a moderate electrophile and moderate nucleophile, while β-phosphorylated analogues of nitroethenes 2a–c can be classified as strong electrophiles and marginal nucleophiles. Moreover, the analysis of CDFT shows that for [3+2] cycloadditions with the participation of β-phosphorylatednitroethene 2a and β-phosphorylated α-cyanonitroethene 2b, the more favored reaction path forms 4-nitro-substituted Δ2-isoxazolines 3a–b, while for a reaction with β-phosphorylated β-cyanonitroethene 2c, the more favored path forms 5-nitro-substituted Δ2-isoxazoline 4c. This is due to the presence of a cyano group in the alkene. The CDFT study correlates well with the analysis of the kinetic description of the considered reaction channels. Moreover, DFT calculations have proven the clearly polar nature of all analyzed [3+2] cycloaddition reactions according to the polar one-step mechanism.

scholarly journals A Computational Study of Direct CO2 Hydrogenation to Methanol on Pd Catalysts

2021 ◽  
Author(s):  
Igor Kowalec ◽  
Lara Kabalan ◽  
Richard Catlow ◽  
Andrew Logsdail
Keyword(s):  
Density Functional ◽  
Negative Charge ◽  
Computational Study ◽  
Adsorbed Species ◽  
Pd Catalysts ◽  
Functional Theory ◽  
Activation Barriers ◽  
Rate Determining Step ◽  
Adsorption Energies ◽  
Insight Into

<p>We investigate the mechanism of direct CO<sub>2</sub> hydrogenation to methanol on Pd (111), (100) and (110) surfaces using density functional theory (DFT), providing insight into the reactivity of CO<sub>2</sub> on Pd-based catalysts. The initial chemisorption of CO<sub>2</sub>, forming a partially charged CO<sub>2</sub><sup>δ-</sup>, is weakly endothermic on a Pd (111) surface, with an adsorption energy of 0.06 eV, and slightly exothermic on Pd (100) and (110) surfaces, with adsorption energies of -0.13 and -0.23 eV, respectively. Based on Mulliken analysis, we attribute the low stability of CO<sub>2</sub><sup>δ-</sup><sub> </sub>on the Pd (111) surface to a negative charge that accumulates on the surface Pd atoms interacting directly with the CO<sub>2</sub><sup>δ-</sup><sub> </sub>adsorbate. For the reaction of the adsorbed species on the Pd surface, HCOOH hydrogenation to H<sub>2</sub>COOH is predicted to be the rate determining step of the conversion to methanol in all cases, with activation barriers of 1.35, 1.26, and 0.92 eV on Pd (111), (100) and (110) surfaces, respectively.<br></p>

A DFT study on the mechanism of reaction between 2, 4-diisocyanatotolune and cellulose

2016 ◽  
Vol 15 (02) ◽  
pp. 1650012 ◽  
Author(s):  
Jiping Cao ◽  
Yali Liu ◽  
Aijuan Shi ◽  
Yuan Yuan ◽  
Mingliang Wang
Keyword(s):  
Reaction Mechanisms ◽  
Energy Barrier ◽  
Density Functional ◽  
Membered Ring ◽  
Functional Theory ◽  
Mechanism Of Reaction ◽  
The Density Functional Theory ◽  
Good Accordance ◽  
Experimental Activation Energy ◽  
Ring Transition State

The reaction mechanisms between 2, 4-Diisocyanatotolune (2, 4-TDI) and cellulose have been investigated using the density functional theory at the B3LYP/6-31[Formula: see text]G (d, p) level. The calculations show that the direct addition of 2, 4-TDI and cellulose possesses an unrealistically high barrier of 32–34[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. With a neighboring [Formula: see text]-d-glucose serving as a proton transporter by forming a flexible six-membered ring transition state, the energy barrier of the reaction is significantly reduced to 16–18 kcal[Formula: see text]mol[Formula: see text], which is in a good accordance with the experimental activation energy of 13.9–16.7[Formula: see text]kcal[Formula: see text]mol[Formula: see text]. It is indicated that the reaction between 2, 4-TDI and cellulose is auto-catalyzed with a neighboring [Formula: see text]-d-glucose acting as a reactive catalyst.

Diyne Cyclization in Camphor Derivatives - Experimental and Theoretical Investigation

1996 ◽  
Vol 51 (11) ◽  
pp. 1655-1662 ◽  
Author(s):  
Gabriele Wagner ◽  
Christian Heiß ◽  
Uwe Verfiirth ◽  
Rudolf Herrmann
Keyword(s):  
Oxygen Atom ◽  
Theoretical Investigation ◽  
Positive Charge ◽  
Membered Ring ◽  
Titanium Chloride ◽  
Nmr Studies ◽  
Methylene Carbon ◽  
Camphor Derivatives ◽  
Exocyclic Methylene ◽  
Derivatives Of

Derivatives of 3-oxo-camphorsulfonimide (1) with two phenylethynyl groups in the endo positions at the carbons C-2 and C-3 were prepared, and their reactivity towards halogenes and titanium chloride was studied. In every case, the two ethynyl groups led to the annulation of a five-membered ring to the bicyclo[2 .2 .1] system in an orientation which depends on the bulkiness of the additional substituent in position 3. NMR studies show that cationic species like 6 and 8 are the first detectable intermediates. They not only contain the fused five-membered ring but also a bond between its exocyclic methylene carbon and an oxygen atom of the sulfonyl group, thus transferring the positive charge mainly to sulfur. Semiempirical calculations (PM3) suggest two intermediates in the formation of such cations.

Computational Study of a Path-Based Algorithm and Its Variants for Static Traffic Assignment

1996 ◽  
Vol 1537 (1) ◽  
pp. 106-115 ◽  
Author(s):  
Carlos Sun ◽  
R. Jayakrishnan ◽  
Wei K. Tsai
Keyword(s):  
Line Search ◽  
Computational Study ◽  
Urban Traffic ◽  
Computer Memory ◽  
Traffic Networks ◽  
Computational Results ◽  
First Derivative ◽  
Line Search Techniques ◽  
Real Time Applications

Recent research has indicated that advances in computer memory have made the use of path-based algorithms in urban traffic networks a possibility. The path-based gradient projection (GP) offers significant benefits in computation times over the conventional Frank-Wolfe algorithm and may be especially suited for real-time applications. The computational results from applying GP to networks of up to 4,900 nodes, as well as the performance of different variants of GP, are discussed. Also discussed is the sensitivity of the results to parameters such as the number of destinations and the level of congestion. The variants of the basic GP algorithm examined are intended to further improve the per-iteration performance of the algorithm for larger networks. These variants include a GP version with a modified first derivative update and different versions that use line-search techniques, including a boundary stopping method. The results establish that GP indicates substantial benefits even for larger networks. The modifications, while they do improve the computation times per GP iteration, affect the convergence quality of the algorithm, indicating that the earlier GP algorithm is a better alternative for both large and small networks.

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